[ViewVC] Diff of: cvs/AnyEvent/README

Comparing AnyEvent/README (file contents):
Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs.
Revision 1.45 by root, Fri Jul 17 14:57:03 2009 UTC

…		…
1	NAME	1	NAME
2	AnyEvent - provide framework for multiple event loops	2	AnyEvent - provide framework for multiple event loops
3		3
4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event	4	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
5	loops	5	event loops.
6		6
7	SYNOPSIS	7	SYNOPSIS
8	use AnyEvent;	8	use AnyEvent;
9		9
		10	# file descriptor readable
10	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub { ... });	11	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
11		12
		13	# one-shot or repeating timers
12	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });	14	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
13	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...	15	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
14		16
15	print AnyEvent->now; # prints current event loop time	17	print AnyEvent->now; # prints current event loop time
16	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.	18	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
17		19
		20	# POSIX signal
18	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });	21	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
19		22
		23	# child process exit
20	my $w = AnyEvent->child (pid => $pid, cb => sub {	24	my $w = AnyEvent->child (pid => $pid, cb => sub {
21	my ($pid, $status) = @_;	25	my ($pid, $status) = @_;
22	...	26	...
23	});	27	});
		28
		29	# called when event loop idle (if applicable)
		30	my $w = AnyEvent->idle (cb => sub { ... });
24		31
25	my $w = AnyEvent->condvar; # stores whether a condition was flagged	32	my $w = AnyEvent->condvar; # stores whether a condition was flagged
26	$w->send; # wake up current and all future recv's	33	$w->send; # wake up current and all future recv's
27	$w->recv; # enters "main loop" till $condvar gets ->send	34	$w->recv; # enters "main loop" till $condvar gets ->send
28	# use a condvar in callback mode:	35	# use a condvar in callback mode:
162		169
163	I/O WATCHERS	170	I/O WATCHERS
164	You can create an I/O watcher by calling the "AnyEvent->io" method with	171	You can create an I/O watcher by calling the "AnyEvent->io" method with
165	the following mandatory key-value pairs as arguments:	172	the following mandatory key-value pairs as arguments:
166		173
167	"fh" is the Perl file handle (not file descriptor) to watch for	174	"fh" is the Perl file handle (or a naked file descriptor) to watch for
168	events (AnyEvent might or might not keep a reference to this file	175	events (AnyEvent might or might not keep a reference to this file
169	handle). Note that only file handles pointing to things for which	176	handle). Note that only file handles pointing to things for which
170	non-blocking operation makes sense are allowed. This includes sockets,	177	non-blocking operation makes sense are allowed. This includes sockets,
171	most character devices, pipes, fifos and so on, but not for example	178	most character devices, pipes, fifos and so on, but not for example
172	files or block devices.	179	files or block devices.
…		…
373		380
374	There is a slight catch to child watchers, however: you usually start	381	There is a slight catch to child watchers, however: you usually start
375	them after the child process was created, and this means the process	382	them after the child process was created, and this means the process
376	could have exited already (and no SIGCHLD will be sent anymore).	383	could have exited already (and no SIGCHLD will be sent anymore).
377		384
378	Not all event models handle this correctly (POE doesn't), but even for	385	Not all event models handle this correctly (neither POE nor IO::Async
		386	do, see their AnyEvent::Impl manpages for details), but even for event
379	event models that do handle this correctly, they usually need to be	387	models that do handle this correctly, they usually need to be loaded
380	loaded before the process exits (i.e. before you fork in the first	388	before the process exits (i.e. before you fork in the first place).
381	place).	389	AnyEvent's pure perl event loop handles all cases correctly regardless
		390	of when you start the watcher.
382		391
383	This means you cannot create a child watcher as the very first thing in	392	This means you cannot create a child watcher as the very first thing in
384	an AnyEvent program, you have to create at least one watcher before	393	an AnyEvent program, you have to create at least one watcher before
385	you "fork" the child (alternatively, you can call "AnyEvent::detect").	394	you "fork" the child (alternatively, you can call "AnyEvent::detect").
386		395
387	Example: fork a process and wait for it	396	Example: fork a process and wait for it
388		397
389	my $done = AnyEvent->condvar;	398	my $done = AnyEvent->condvar;
390		399
391	my $pid = fork or exit 5;	400	my $pid = fork or exit 5;
392		401
393	my $w = AnyEvent->child (	402	my $w = AnyEvent->child (
394	pid => $pid,	403	pid => $pid,
395	cb => sub {	404	cb => sub {
396	my ($pid, $status) = @_;	405	my ($pid, $status) = @_;
397	warn "pid $pid exited with status $status";	406	warn "pid $pid exited with status $status";
398	$done->send;	407	$done->send;
399	},	408	},
400	);	409	);
401		410
402	# do something else, then wait for process exit	411	# do something else, then wait for process exit
403	$done->recv;	412	$done->recv;
		413
		414	IDLE WATCHERS
		415	Sometimes there is a need to do something, but it is not so important to
		416	do it instantly, but only when there is nothing better to do. This
		417	"nothing better to do" is usually defined to be "no other events need
		418	attention by the event loop".
		419
		420	Idle watchers ideally get invoked when the event loop has nothing better
		421	to do, just before it would block the process to wait for new events.
		422	Instead of blocking, the idle watcher is invoked.
		423
		424	Most event loops unfortunately do not really support idle watchers (only
		425	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		426	will simply call the callback "from time to time".
		427
		428	Example: read lines from STDIN, but only process them when the program
		429	is otherwise idle:
		430
		431	my @lines; # read data
		432	my $idle_w;
		433	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		434	push @lines, scalar <STDIN>;
		435
		436	# start an idle watcher, if not already done
		437	$idle_w \|\|= AnyEvent->idle (cb => sub {
		438	# handle only one line, when there are lines left
		439	if (my $line = shift @lines) {
		440	print "handled when idle: $line";
		441	} else {
		442	# otherwise disable the idle watcher again
		443	undef $idle_w;
		444	}
		445	});
		446	});
404		447
405	CONDITION VARIABLES	448	CONDITION VARIABLES
406	If you are familiar with some event loops you will know that all of them	449	If you are familiar with some event loops you will know that all of them
407	require you to run some blocking "loop", "run" or similar function that	450	require you to run some blocking "loop", "run" or similar function that
408	will actively watch for new events and call your callbacks.	451	will actively watch for new events and call your callbacks.
409		452
410	AnyEvent is different, it expects somebody else to run the event loop	453	AnyEvent is slightly different: it expects somebody else to run the
411	and will only block when necessary (usually when told by the user).	454	event loop and will only block when necessary (usually when told by the
		455	user).
412		456
413	The instrument to do that is called a "condition variable", so called	457	The instrument to do that is called a "condition variable", so called
414	because they represent a condition that must become true.	458	because they represent a condition that must become true.
415		459
		460	Now is probably a good time to look at the examples further below.
		461
416	Condition variables can be created by calling the "AnyEvent->condvar"	462	Condition variables can be created by calling the "AnyEvent->condvar"
417	method, usually without arguments. The only argument pair allowed is	463	method, usually without arguments. The only argument pair allowed is
418
419	"cb", which specifies a callback to be called when the condition	464	"cb", which specifies a callback to be called when the condition
420	variable becomes true, with the condition variable as the first argument	465	variable becomes true, with the condition variable as the first argument
421	(but not the results).	466	(but not the results).
422		467
423	After creation, the condition variable is "false" until it becomes	468	After creation, the condition variable is "false" until it becomes
…		…
472	after => 1,	517	after => 1,
473	cb => sub { $result_ready->send },	518	cb => sub { $result_ready->send },
474	);	519	);
475		520
476	# this "blocks" (while handling events) till the callback	521	# this "blocks" (while handling events) till the callback
477	# calls send	522	# calls -<send
478	$result_ready->recv;	523	$result_ready->recv;
479		524
480	Example: wait for a timer, but take advantage of the fact that condition	525	Example: wait for a timer, but take advantage of the fact that condition
481	variables are also code references.	526	variables are also callable directly.
482		527
483	my $done = AnyEvent->condvar;	528	my $done = AnyEvent->condvar;
484	my $delay = AnyEvent->timer (after => 5, cb => $done);	529	my $delay = AnyEvent->timer (after => 5, cb => $done);
485	$done->recv;	530	$done->recv;
486		531
…		…
492		537
493	...	538	...
494		539
495	my @info = $couchdb->info->recv;	540	my @info = $couchdb->info->recv;
496		541
497	And this is how you would just ste a callback to be called whenever the	542	And this is how you would just set a callback to be called whenever the
498	results are available:	543	results are available:
499		544
500	$couchdb->info->cb (sub {	545	$couchdb->info->cb (sub {
501	my @info = $_[0]->recv;	546	my @info = $_[0]->recv;
502	});	547	});
…		…
517		562
518	Any arguments passed to the "send" call will be returned by all	563	Any arguments passed to the "send" call will be returned by all
519	future "->recv" calls.	564	future "->recv" calls.
520		565
521	Condition variables are overloaded so one can call them directly (as	566	Condition variables are overloaded so one can call them directly (as
522	a code reference). Calling them directly is the same as calling	567	if they were a code reference). Calling them directly is the same as
523	"send". Note, however, that many C-based event loops do not handle	568	calling "send".
524	overloading, so as tempting as it may be, passing a condition
525	variable instead of a callback does not work. Both the pure perl and
526	EV loops support overloading, however, as well as all functions that
527	use perl to invoke a callback (as in AnyEvent::Socket and
528	AnyEvent::DNS for example).
529		569
530	$cv->croak ($error)	570	$cv->croak ($error)
531	Similar to send, but causes all call's to "->recv" to invoke	571	Similar to send, but causes all call's to "->recv" to invoke
532	"Carp::croak" with the given error message/object/scalar.	572	"Carp::croak" with the given error message/object/scalar.
533		573
534	This can be used to signal any errors to the condition variable	574	This can be used to signal any errors to the condition variable
535	user/consumer.	575	user/consumer. Doing it this way instead of calling "croak" directly
		576	delays the error detetcion, but has the overwhelmign advantage that
		577	it diagnoses the error at the place where the result is expected,
		578	and not deep in some event clalback without connection to the actual
		579	code causing the problem.
536		580
537	$cv->begin ([group callback])	581	$cv->begin ([group callback])
538	$cv->end	582	$cv->end
539	These two methods are EXPERIMENTAL and MIGHT CHANGE.
540
541	These two methods can be used to combine many transactions/events	583	These two methods can be used to combine many transactions/events
542	into one. For example, a function that pings many hosts in parallel	584	into one. For example, a function that pings many hosts in parallel
543	might want to use a condition variable for the whole process.	585	might want to use a condition variable for the whole process.
544		586
545	Every call to "->begin" will increment a counter, and every call to	587	Every call to "->begin" will increment a counter, and every call to
546	"->end" will decrement it. If the counter reaches 0 in "->end", the	588	"->end" will decrement it. If the counter reaches 0 in "->end", the
547	(last) callback passed to "begin" will be executed. That callback is	589	(last) callback passed to "begin" will be executed. That callback is
548	supposed to call "->send", but that is not required. If no	590	supposed to call "->send", but that is not required. If no
549	callback was set, "send" will be called without any arguments.	591	callback was set, "send" will be called without any arguments.
550		592
551	Let's clarify this with the ping example:	593	You can think of "$cv->send" giving you an OR condition (one call
		594	sends), while "$cv->begin" and "$cv->end" giving you an AND
		595	condition (all "begin" calls must be "end"'ed before the condvar
		596	sends).
		597
		598	Let's start with a simple example: you have two I/O watchers (for
		599	example, STDOUT and STDERR for a program), and you want to wait for
		600	both streams to close before activating a condvar:
		601
		602	my $cv = AnyEvent->condvar;
		603
		604	$cv->begin; # first watcher
		605	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		606	defined sysread $fh1, my $buf, 4096
		607	or $cv->end;
		608	});
		609
		610	$cv->begin; # second watcher
		611	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		612	defined sysread $fh2, my $buf, 4096
		613	or $cv->end;
		614	});
		615
		616	$cv->recv;
		617
		618	This works because for every event source (EOF on file handle),
		619	there is one call to "begin", so the condvar waits for all calls to
		620	"end" before sending.
		621
		622	The ping example mentioned above is slightly more complicated, as
		623	the there are results to be passwd back, and the number of tasks
		624	that are begung can potentially be zero:
552		625
553	my $cv = AnyEvent->condvar;	626	my $cv = AnyEvent->condvar;
554		627
555	my %result;	628	my %result;
556	$cv->begin (sub { $cv->send (\%result) });	629	$cv->begin (sub { $cv->send (\%result) });
…		…
576	the loop, which serves two important purposes: first, it sets the	649	the loop, which serves two important purposes: first, it sets the
577	callback to be called once the counter reaches 0, and second, it	650	callback to be called once the counter reaches 0, and second, it
578	ensures that "send" is called even when "no" hosts are being pinged	651	ensures that "send" is called even when "no" hosts are being pinged
579	(the loop doesn't execute once).	652	(the loop doesn't execute once).
580		653
581	This is the general pattern when you "fan out" into multiple	654	This is the general pattern when you "fan out" into multiple (but
582	subrequests: use an outer "begin"/"end" pair to set the callback and	655	potentially none) subrequests: use an outer "begin"/"end" pair to
583	ensure "end" is called at least once, and then, for each subrequest	656	set the callback and ensure "end" is called at least once, and then,
584	you start, call "begin" and for each subrequest you finish, call	657	for each subrequest you start, call "begin" and for each subrequest
585	"end".	658	you finish, call "end".
586		659
587	METHODS FOR CONSUMERS	660	METHODS FOR CONSUMERS
588	These methods should only be used by the consuming side, i.e. the code	661	These methods should only be used by the consuming side, i.e. the code
589	awaits the condition.	662	awaits the condition.
590		663
…		…
599	function will call "croak".	672	function will call "croak".
600		673
601	In list context, all parameters passed to "send" will be returned,	674	In list context, all parameters passed to "send" will be returned,
602	in scalar context only the first one will be returned.	675	in scalar context only the first one will be returned.
603		676
		677	Note that doing a blocking wait in a callback is not supported by
		678	any event loop, that is, recursive invocation of a blocking "->recv"
		679	is not allowed, and the "recv" call will "croak" if such a condition
		680	is detected. This condition can be slightly loosened by using
		681	Coro::AnyEvent, which allows you to do a blocking "->recv" from any
		682	thread that doesn't run the event loop itself.
		683
604	Not all event models support a blocking wait - some die in that case	684	Not all event models support a blocking wait - some die in that case
605	(programs might want to do that to stay interactive), so *if you are	685	(programs might want to do that to stay interactive), so *if you are
606	using this from a module, never require a blocking wait*, but let	686	using this from a module, never require a blocking wait*. Instead,
607	the caller decide whether the call will block or not (for example,	687	let the caller decide whether the call will block or not (for
608	by coupling condition variables with some kind of request results	688	example, by coupling condition variables with some kind of request
609	and supporting callbacks so the caller knows that getting the result	689	results and supporting callbacks so the caller knows that getting
610	will not block, while still supporting blocking waits if the caller	690	the result will not block, while still supporting blocking waits if
611	so desires).	691	the caller so desires).
612
613	Another reason never to "->recv" in a module is that you cannot
614	sensibly have two "->recv"'s in parallel, as that would require
615	multiple interpreters or coroutines/threads, none of which
616	"AnyEvent" can supply.
617
618	The Coro module, however, can and does supply coroutines and, in
619	fact, Coro::AnyEvent replaces AnyEvent's condvars by coroutine-safe
620	versions and also integrates coroutines into AnyEvent, making
621	blocking "->recv" calls perfectly safe as long as they are done from
622	another coroutine (one that doesn't run the event loop).
623		692
624	You can ensure that "-recv" never blocks by setting a callback and	693	You can ensure that "-recv" never blocks by setting a callback and
625	only calling "->recv" from within that callback (or at a later	694	only calling "->recv" from within that callback (or at a later
626	time). This will work even when the event loop does not support	695	time). This will work even when the event loop does not support
627	blocking waits otherwise.	696	blocking waits otherwise.
…		…
637	The callback will be called when the condition becomes "true", i.e.	706	The callback will be called when the condition becomes "true", i.e.
638	when "send" or "croak" are called, with the only argument being the	707	when "send" or "croak" are called, with the only argument being the
639	condition variable itself. Calling "recv" inside the callback or at	708	condition variable itself. Calling "recv" inside the callback or at
640	any later time is guaranteed not to block.	709	any later time is guaranteed not to block.
641		710
		711	SUPPORTED EVENT LOOPS/BACKENDS
		712	The available backend classes are (every class has its own manpage):
		713
		714	Backends that are autoprobed when no other event loop can be found.
		715	EV is the preferred backend when no other event loop seems to be in
		716	use. If EV is not installed, then AnyEvent will try Event, and,
		717	failing that, will fall back to its own pure-perl implementation,
		718	which is available everywhere as it comes with AnyEvent itself.
		719
		720	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		721	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		722	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		723
		724	Backends that are transparently being picked up when they are used.
		725	These will be used when they are currently loaded when the first
		726	watcher is created, in which case it is assumed that the application
		727	is using them. This means that AnyEvent will automatically pick the
		728	right backend when the main program loads an event module before
		729	anything starts to create watchers. Nothing special needs to be done
		730	by the main program.
		731
		732	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		733	AnyEvent::Impl::Tk based on Tk, very broken.
		734	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		735	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		736
		737	Backends with special needs.
		738	Qt requires the Qt::Application to be instantiated first, but will
		739	otherwise be picked up automatically. As long as the main program
		740	instantiates the application before any AnyEvent watchers are
		741	created, everything should just work.
		742
		743	AnyEvent::Impl::Qt based on Qt.
		744
		745	Support for IO::Async can only be partial, as it is too broken and
		746	architecturally limited to even support the AnyEvent API. It also is
		747	the only event loop that needs the loop to be set explicitly, so it
		748	can only be used by a main program knowing about AnyEvent. See
		749	AnyEvent::Impl::Async for the gory details.
		750
		751	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		752
		753	Event loops that are indirectly supported via other backends.
		754	Some event loops can be supported via other modules:
		755
		756	There is no direct support for WxWidgets (Wx) or Prima.
		757
		758	WxWidgets has no support for watching file handles. However, you can
		759	use WxWidgets through the POE adaptor, as POE has a Wx backend that
		760	simply polls 20 times per second, which was considered to be too
		761	horrible to even consider for AnyEvent.
		762
		763	Prima is not supported as nobody seems to be using it, but it has a
		764	POE backend, so it can be supported through POE.
		765
		766	AnyEvent knows about both Prima and Wx, however, and will try to
		767	load POE when detecting them, in the hope that POE will pick them
		768	up, in which case everything will be automatic.
		769
642	GLOBAL VARIABLES AND FUNCTIONS	770	GLOBAL VARIABLES AND FUNCTIONS
		771	These are not normally required to use AnyEvent, but can be useful to
		772	write AnyEvent extension modules.
		773
643	$AnyEvent::MODEL	774	$AnyEvent::MODEL
644	Contains "undef" until the first watcher is being created. Then it	775	Contains "undef" until the first watcher is being created, before
		776	the backend has been autodetected.
		777
645	contains the event model that is being used, which is the name of	778	Afterwards it contains the event model that is being used, which is
646	the Perl class implementing the model. This class is usually one of	779	the name of the Perl class implementing the model. This class is
647	the "AnyEvent::Impl:xxx" modules, but can be any other class in the	780	usually one of the "AnyEvent::Impl:xxx" modules, but can be any
648	case AnyEvent has been extended at runtime (e.g. in rxvt-unicode).	781	other class in the case AnyEvent has been extended at runtime (e.g.
649		782	in rxvt-unicode it will be "urxvt::anyevent").
650	The known classes so far are:
651
652	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
653	AnyEvent::Impl::Event based on Event, second best choice.
654	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
655	AnyEvent::Impl::Glib based on Glib, third-best choice.
656	AnyEvent::Impl::Tk based on Tk, very bad choice.
657	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
658	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
659	AnyEvent::Impl::POE based on POE, not generic enough for full support.
660
661	There is no support for WxWidgets, as WxWidgets has no support for
662	watching file handles. However, you can use WxWidgets through the
663	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
664	second, which was considered to be too horrible to even consider for
665	AnyEvent. Likewise, other POE backends can be used by AnyEvent by
666	using it's adaptor.
667
668	AnyEvent knows about Prima and Wx and will try to use POE when
669	autodetecting them.
670		783
671	AnyEvent::detect	784	AnyEvent::detect
672	Returns $AnyEvent::MODEL, forcing autodetection of the event model	785	Returns $AnyEvent::MODEL, forcing autodetection of the event model
673	if necessary. You should only call this function right before you	786	if necessary. You should only call this function right before you
674	would have created an AnyEvent watcher anyway, that is, as late as	787	would have created an AnyEvent watcher anyway, that is, as late as
675	possible at runtime.	788	possible at runtime, and not e.g. while initialising of your module.
		789
		790	If you need to do some initialisation before AnyEvent watchers are
		791	created, use "post_detect".
676		792
677	$guard = AnyEvent::post_detect { BLOCK }	793	$guard = AnyEvent::post_detect { BLOCK }
678	Arranges for the code block to be executed as soon as the event	794	Arranges for the code block to be executed as soon as the event
679	model is autodetected (or immediately if this has already happened).	795	model is autodetected (or immediately if this has already happened).
		796
		797	The block will be executed after the actual backend has been
		798	detected ($AnyEvent::MODEL is set), but before any watchers have
		799	been created, so it is possible to e.g. patch @AnyEvent::ISA or do
		800	other initialisations - see the sources of AnyEvent::Strict or
		801	AnyEvent::AIO to see how this is used.
		802
		803	The most common usage is to create some global watchers, without
		804	forcing event module detection too early, for example, AnyEvent::AIO
		805	creates and installs the global IO::AIO watcher in a "post_detect"
		806	block to avoid autodetecting the event module at load time.
680		807
681	If called in scalar or list context, then it creates and returns an	808	If called in scalar or list context, then it creates and returns an
682	object that automatically removes the callback again when it is	809	object that automatically removes the callback again when it is
683	destroyed. See Coro::BDB for a case where this is useful.	810	destroyed. See Coro::BDB for a case where this is useful.
684		811
…		…
686	If there are any code references in this array (you can "push" to it	813	If there are any code references in this array (you can "push" to it
687	before or after loading AnyEvent), then they will called directly	814	before or after loading AnyEvent), then they will called directly
688	after the event loop has been chosen.	815	after the event loop has been chosen.
689		816
690	You should check $AnyEvent::MODEL before adding to this array,	817	You should check $AnyEvent::MODEL before adding to this array,
691	though: if it contains a true value then the event loop has already	818	though: if it is defined then the event loop has already been
692	been detected, and the array will be ignored.	819	detected, and the array will be ignored.
693		820
694	Best use "AnyEvent::post_detect { BLOCK }" instead.	821	Best use "AnyEvent::post_detect { BLOCK }" when your application
		822	allows it,as it takes care of these details.
		823
		824	This variable is mainly useful for modules that can do something
		825	useful when AnyEvent is used and thus want to know when it is
		826	initialised, but do not need to even load it by default. This array
		827	provides the means to hook into AnyEvent passively, without loading
		828	it.
695		829
696	WHAT TO DO IN A MODULE	830	WHAT TO DO IN A MODULE
697	As a module author, you should "use AnyEvent" and call AnyEvent methods	831	As a module author, you should "use AnyEvent" and call AnyEvent methods
698	freely, but you should not load a specific event module or rely on it.	832	freely, but you should not load a specific event module or rely on it.
699		833
…		…
750	variable somewhere, waiting for it, and sending it when the program	884	variable somewhere, waiting for it, and sending it when the program
751	should exit cleanly.	885	should exit cleanly.
752		886
753	OTHER MODULES	887	OTHER MODULES
754	The following is a non-exhaustive list of additional modules that use	888	The following is a non-exhaustive list of additional modules that use
755	AnyEvent and can therefore be mixed easily with other AnyEvent modules	889	AnyEvent as a client and can therefore be mixed easily with other
756	in the same program. Some of the modules come with AnyEvent, some are	890	AnyEvent modules and other event loops in the same program. Some of the
757	available via CPAN.	891	modules come with AnyEvent, most are available via CPAN.
758		892
759	AnyEvent::Util	893	AnyEvent::Util
760	Contains various utility functions that replace often-used but	894	Contains various utility functions that replace often-used but
761	blocking functions such as "inet_aton" by event-/callback-based	895	blocking functions such as "inet_aton" by event-/callback-based
762	versions.	896	versions.
…		…
768	more.	902	more.
769		903
770	AnyEvent::Handle	904	AnyEvent::Handle
771	Provide read and write buffers, manages watchers for reads and	905	Provide read and write buffers, manages watchers for reads and
772	writes, supports raw and formatted I/O, I/O queued and fully	906	writes, supports raw and formatted I/O, I/O queued and fully
773	transparent and non-blocking SSL/TLS.	907	transparent and non-blocking SSL/TLS (via AnyEvent::TLS.
774		908
775	AnyEvent::DNS	909	AnyEvent::DNS
776	Provides rich asynchronous DNS resolver capabilities.	910	Provides rich asynchronous DNS resolver capabilities.
777		911
778	AnyEvent::HTTP	912	AnyEvent::HTTP
…		…
799		933
800	AnyEvent::GPSD	934	AnyEvent::GPSD
801	A non-blocking interface to gpsd, a daemon delivering GPS	935	A non-blocking interface to gpsd, a daemon delivering GPS
802	information.	936	information.
803		937
		938	AnyEvent::IRC
		939	AnyEvent based IRC client module family (replacing the older
		940	Net::IRC3).
		941
		942	AnyEvent::XMPP
		943	AnyEvent based XMPP (Jabber protocol) module family (replacing the
		944	older Net::XMPP2>.
		945
804	AnyEvent::IGS	946	AnyEvent::IGS
805	A non-blocking interface to the Internet Go Server protocol (used by	947	A non-blocking interface to the Internet Go Server protocol (used by
806	App::IGS).	948	App::IGS).
807		949
808	AnyEvent::IRC
809	AnyEvent based IRC client module family (replacing the older
810	Net::IRC3).
811
812	Net::XMPP2
813	AnyEvent based XMPP (Jabber protocol) module family.
814
815	Net::FCP	950	Net::FCP
816	AnyEvent-based implementation of the Freenet Client Protocol,	951	AnyEvent-based implementation of the Freenet Client Protocol,
817	birthplace of AnyEvent.	952	birthplace of AnyEvent.
818		953
819	Event::ExecFlow	954	Event::ExecFlow
820	High level API for event-based execution flow control.	955	High level API for event-based execution flow control.
821		956
822	Coro	957	Coro
823	Has special support for AnyEvent via Coro::AnyEvent.	958	Has special support for AnyEvent via Coro::AnyEvent.
824
825	IO::Lambda
826	The lambda approach to I/O - don't ask, look there. Can use
827	AnyEvent.
828		959
829	ERROR AND EXCEPTION HANDLING	960	ERROR AND EXCEPTION HANDLING
830	In general, AnyEvent does not do any error handling - it relies on the	961	In general, AnyEvent does not do any error handling - it relies on the
831	caller to do that if required. The AnyEvent::Strict module (see also the	962	caller to do that if required. The AnyEvent::Strict module (see also the
832	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict	963	"PERL_ANYEVENT_STRICT" environment variable, below) provides strict
…		…
842	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",	973	"condvar->recv"), the Event and EV modules call "$Event/EV::DIED->()",
843	Glib uses "install_exception_handler" and so on.	974	Glib uses "install_exception_handler" and so on.
844		975
845	ENVIRONMENT VARIABLES	976	ENVIRONMENT VARIABLES
846	The following environment variables are used by this module or its	977	The following environment variables are used by this module or its
847	submodules:	978	submodules.
		979
		980	Note that AnyEvent will remove all environment variables starting with
		981	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		982	enabled.
848		983
849	"PERL_ANYEVENT_VERBOSE"	984	"PERL_ANYEVENT_VERBOSE"
850	By default, AnyEvent will be completely silent except in fatal	985	By default, AnyEvent will be completely silent except in fatal
851	conditions. You can set this environment variable to make AnyEvent	986	conditions. You can set this environment variable to make AnyEvent
852	more talkative.	987	more talkative.
…		…
861	"PERL_ANYEVENT_STRICT"	996	"PERL_ANYEVENT_STRICT"
862	AnyEvent does not do much argument checking by default, as thorough	997	AnyEvent does not do much argument checking by default, as thorough
863	argument checking is very costly. Setting this variable to a true	998	argument checking is very costly. Setting this variable to a true
864	value will cause AnyEvent to load "AnyEvent::Strict" and then to	999	value will cause AnyEvent to load "AnyEvent::Strict" and then to
865	thoroughly check the arguments passed to most method calls. If it	1000	thoroughly check the arguments passed to most method calls. If it
866	finds any problems it will croak.	1001	finds any problems, it will croak.
867		1002
868	In other words, enables "strict" mode.	1003	In other words, enables "strict" mode.
869		1004
870	Unlike "use strict", it is definitely recommended ot keep it off in	1005	Unlike "use strict", it is definitely recommended to keep it off in
871	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment	1006	production. Keeping "PERL_ANYEVENT_STRICT=1" in your environment
872	while developing programs can be very useful, however.	1007	while developing programs can be very useful, however.
873		1008
874	"PERL_ANYEVENT_MODEL"	1009	"PERL_ANYEVENT_MODEL"
875	This can be used to specify the event model to be used by AnyEvent,	1010	This can be used to specify the event model to be used by AnyEvent,
…		…
918	EDNS0 in its DNS requests.	1053	EDNS0 in its DNS requests.
919		1054
920	"PERL_ANYEVENT_MAX_FORKS"	1055	"PERL_ANYEVENT_MAX_FORKS"
921	The maximum number of child processes that	1056	The maximum number of child processes that
922	"AnyEvent::Util::fork_call" will create in parallel.	1057	"AnyEvent::Util::fork_call" will create in parallel.
		1058
		1059	"PERL_ANYEVENT_MAX_OUTSTANDING_DNS"
		1060	The default value for the "max_outstanding" parameter for the
		1061	default DNS resolver - this is the maximum number of parallel DNS
		1062	requests that are sent to the DNS server.
		1063
		1064	"PERL_ANYEVENT_RESOLV_CONF"
		1065	The file to use instead of /etc/resolv.conf (or OS-specific
		1066	configuration) in the default resolver. When set to the empty
		1067	string, no default config will be used.
		1068
		1069	"PERL_ANYEVENT_CA_FILE", "PERL_ANYEVENT_CA_PATH".
		1070	When neither "ca_file" nor "ca_path" was specified during
		1071	AnyEvent::TLS context creation, and either of these environment
		1072	variables exist, they will be used to specify CA certificate
		1073	locations instead of a system-dependent default.
923		1074
924	SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1075	SUPPLYING YOUR OWN EVENT MODEL INTERFACE
925	This is an advanced topic that you do not normally need to use AnyEvent	1076	This is an advanced topic that you do not normally need to use AnyEvent
926	in a module. This section is only of use to event loop authors who want	1077	in a module. This section is only of use to event loop authors who want
927	to provide AnyEvent compatibility.	1078	to provide AnyEvent compatibility.
…		…
1163	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers	1314	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1164	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal	1315	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1165	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation	1316	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1166	Event/Event 16000 517 32.20 31.80 0.81 Event native interface	1317	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1167	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers	1318	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1319	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1320	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1168	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour	1321	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1169	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers	1322	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1170	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event	1323	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1171	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select	1324	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1172		1325
…		…
1201	few of them active), of course, but this was not subject of this	1354	few of them active), of course, but this was not subject of this
1202	benchmark.	1355	benchmark.
1203		1356
1204	The "Event" module has a relatively high setup and callback invocation	1357	The "Event" module has a relatively high setup and callback invocation
1205	cost, but overall scores in on the third place.	1358	cost, but overall scores in on the third place.
		1359
		1360	"IO::Async" performs admirably well, about on par with "Event", even
		1361	when using its pure perl backend.
1206		1362
1207	"Glib"'s memory usage is quite a bit higher, but it features a faster	1363	"Glib"'s memory usage is quite a bit higher, but it features a faster
1208	callback invocation and overall ends up in the same class as "Event".	1364	callback invocation and overall ends up in the same class as "Event".
1209	However, Glib scales extremely badly, doubling the number of watchers	1365	However, Glib scales extremely badly, doubling the number of watchers
1210	increases the processing time by more than a factor of four, making it	1366	increases the processing time by more than a factor of four, making it
…		…
1281	single "request", that is, reading the token from the pipe and	1437	single "request", that is, reading the token from the pipe and
1282	forwarding it to another server. This includes deleting the old timeout	1438	forwarding it to another server. This includes deleting the old timeout
1283	and creating a new one that moves the timeout into the future.	1439	and creating a new one that moves the timeout into the future.
1284		1440
1285	Results	1441	Results
1286	name sockets create request	1442	name sockets create request
1287	EV 20000 69.01 11.16	1443	EV 20000 69.01 11.16
1288	Perl 20000 73.32 35.87	1444	Perl 20000 73.32 35.87
		1445	IOAsync 20000 157.00 98.14 epoll
		1446	IOAsync 20000 159.31 616.06 poll
1289	Event 20000 212.62 257.32	1447	Event 20000 212.62 257.32
1290	Glib 20000 651.16 1896.30	1448	Glib 20000 651.16 1896.30
1291	POE 20000 349.67 12317.24 uses POE::Loop::Event	1449	POE 20000 349.67 12317.24 uses POE::Loop::Event
1292		1450
1293	Discussion	1451	Discussion
1294	This benchmark does measure scalability and overall performance of the	1452	This benchmark does measure scalability and overall performance of the
1295	particular event loop.	1453	particular event loop.
1296		1454
1297	EV is again fastest. Since it is using epoll on my system, the setup	1455	EV is again fastest. Since it is using epoll on my system, the setup
1298	time is relatively high, though.	1456	time is relatively high, though.
1299		1457
1300	Perl surprisingly comes second. It is much faster than the C-based event	1458	Perl surprisingly comes second. It is much faster than the C-based event
1301	loops Event and Glib.	1459	loops Event and Glib.
		1460
		1461	IO::Async performs very well when using its epoll backend, and still
		1462	quite good compared to Glib when using its pure perl backend.
1302		1463
1303	Event suffers from high setup time as well (look at its code and you	1464	Event suffers from high setup time as well (look at its code and you
1304	will understand why). Callback invocation also has a high overhead	1465	will understand why). Callback invocation also has a high overhead
1305	compared to the "$_->() for .."-style loop that the Perl event loop	1466	compared to the "$_->() for .."-style loop that the Perl event loop
1306	uses. Event uses select or poll in basically all documented	1467	uses. Event uses select or poll in basically all documented
…		…
1357		1518
1358	Summary	1519	Summary
1359	* C-based event loops perform very well with small number of watchers,	1520	* C-based event loops perform very well with small number of watchers,
1360	as the management overhead dominates.	1521	as the management overhead dominates.
1361		1522
		1523	THE IO::Lambda BENCHMARK
		1524	Recently I was told about the benchmark in the IO::Lambda manpage, which
		1525	could be misinterpreted to make AnyEvent look bad. In fact, the
		1526	benchmark simply compares IO::Lambda with POE, and IO::Lambda looks
		1527	better (which shouldn't come as a surprise to anybody). As such, the
		1528	benchmark is fine, and mostly shows that the AnyEvent backend from
		1529	IO::Lambda isn't very optimal. But how would AnyEvent compare when used
		1530	without the extra baggage? To explore this, I wrote the equivalent
		1531	benchmark for AnyEvent.
		1532
		1533	The benchmark itself creates an echo-server, and then, for 500 times,
		1534	connects to the echo server, sends a line, waits for the reply, and then
		1535	creates the next connection. This is a rather bad benchmark, as it
		1536	doesn't test the efficiency of the framework or much non-blocking I/O,
		1537	but it is a benchmark nevertheless.
		1538
		1539	name runtime
		1540	Lambda/select 0.330 sec
		1541	+ optimized 0.122 sec
		1542	Lambda/AnyEvent 0.327 sec
		1543	+ optimized 0.138 sec
		1544	Raw sockets/select 0.077 sec
		1545	POE/select, components 0.662 sec
		1546	POE/select, raw sockets 0.226 sec
		1547	POE/select, optimized 0.404 sec
		1548
		1549	AnyEvent/select/nb 0.085 sec
		1550	AnyEvent/EV/nb 0.068 sec
		1551	+state machine 0.134 sec
		1552
		1553	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		1554	benchmarks actually make blocking connects and use 100% blocking I/O,
		1555	defeating the purpose of an event-based solution. All of the newly
		1556	written AnyEvent benchmarks use 100% non-blocking connects (using
		1557	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		1558	resolver), so AnyEvent is at a disadvantage here, as non-blocking
		1559	connects generally require a lot more bookkeeping and event handling
		1560	than blocking connects (which involve a single syscall only).
		1561
		1562	The last AnyEvent benchmark additionally uses AnyEvent::Handle, which
		1563	offers similar expressive power as POE and IO::Lambda, using
		1564	conventional Perl syntax. This means that both the echo server and the
		1565	client are 100% non-blocking, further placing it at a disadvantage.
		1566
		1567	As you can see, the AnyEvent + EV combination even beats the
		1568	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		1569	backend easily beats IO::Lambda and POE.
		1570
		1571	And even the 100% non-blocking version written using the high-level (and
		1572	slow :) AnyEvent::Handle abstraction beats both POE and IO::Lambda by a
		1573	large margin, even though it does all of DNS, tcp-connect and socket I/O
		1574	in a non-blocking way.
		1575
		1576	The two AnyEvent benchmarks programs can be found as eg/ae0.pl and
		1577	eg/ae2.pl in the AnyEvent distribution, the remaining benchmarks are
		1578	part of the IO::lambda distribution and were used without any changes.
		1579
1362	SIGNALS	1580	SIGNALS
1363	AnyEvent currently installs handlers for these signals:	1581	AnyEvent currently installs handlers for these signals:
1364		1582
1365	SIGCHLD	1583	SIGCHLD
1366	A handler for "SIGCHLD" is installed by AnyEvent's child watcher	1584	A handler for "SIGCHLD" is installed by AnyEvent's child watcher
1367	emulation for event loops that do not support them natively. Also,	1585	emulation for event loops that do not support them natively. Also,
1368	some event loops install a similar handler.	1586	some event loops install a similar handler.
		1587
		1588	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE,
		1589	then AnyEvent will reset it to default, to avoid losing child exit
		1590	statuses.
1369		1591
1370	SIGPIPE	1592	SIGPIPE
1371	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is	1593	A no-op handler is installed for "SIGPIPE" when $SIG{PIPE} is
1372	"undef" when AnyEvent gets loaded.	1594	"undef" when AnyEvent gets loaded.
1373		1595
…		…
1401		1623
1402	You can make AnyEvent completely ignore this variable by deleting it	1624	You can make AnyEvent completely ignore this variable by deleting it
1403	before the first watcher gets created, e.g. with a "BEGIN" block:	1625	before the first watcher gets created, e.g. with a "BEGIN" block:
1404		1626
1405	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	1627	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1406		1628
1407	use AnyEvent;	1629	use AnyEvent;
1408		1630
1409	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	1631	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1410	be used to probe what backend is used and gain other information (which	1632	be used to probe what backend is used and gain other information (which
1411	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),	1633	is probably even less useful to an attacker than PERL_ANYEVENT_MODEL),
1412	and $ENV{PERL_ANYEGENT_STRICT}.	1634	and $ENV{PERL_ANYEVENT_STRICT}.
		1635
		1636	Note that AnyEvent will remove all environment variables starting with
		1637	"PERL_ANYEVENT_" from %ENV when it is loaded while taint mode is
		1638	enabled.
1413		1639
1414	BUGS	1640	BUGS
1415	Perl 5.8 has numerous memleaks that sometimes hit this module and are	1641	Perl 5.8 has numerous memleaks that sometimes hit this module and are
1416	hard to work around. If you suffer from memleaks, first upgrade to Perl	1642	hard to work around. If you suffer from memleaks, first upgrade to Perl
1417	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other	1643	5.10 and check wether the leaks still show up. (Perl 5.10.0 has other
…		…
1424	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,	1650	Event modules: EV, EV::Glib, Glib::EV, Event, Glib::Event, Glib, Tk,
1425	Event::Lib, Qt, POE.	1651	Event::Lib, Qt, POE.
1426		1652
1427	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,	1653	Implementations: AnyEvent::Impl::EV, AnyEvent::Impl::Event,
1428	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,	1654	AnyEvent::Impl::Glib, AnyEvent::Impl::Tk, AnyEvent::Impl::Perl,
1429	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE.	1655	AnyEvent::Impl::EventLib, AnyEvent::Impl::Qt, AnyEvent::Impl::POE,
		1656	AnyEvent::Impl::IOAsync.
1430		1657
1431	Non-blocking file handles, sockets, TCP clients and servers:	1658	Non-blocking file handles, sockets, TCP clients and servers:
1432	AnyEvent::Handle, AnyEvent::Socket.	1659	AnyEvent::Handle, AnyEvent::Socket, AnyEvent::TLS.
1433		1660
1434	Asynchronous DNS: AnyEvent::DNS.	1661	Asynchronous DNS: AnyEvent::DNS.
1435		1662
1436	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,	1663	Coroutine support: Coro, Coro::AnyEvent, Coro::EV, Coro::Event,
1437		1664
1438	Nontrivial usage examples: Net::FCP, Net::XMPP2, AnyEvent::DNS.	1665	Nontrivial usage examples: AnyEvent::GPSD, AnyEvent::XMPP,
		1666	AnyEvent::HTTP.
1439		1667
1440	AUTHOR	1668	AUTHOR
1441	Marc Lehmann <schmorp@schmorp.de>	1669	Marc Lehmann <schmorp@schmorp.de>
1442	http://home.schmorp.de/	1670	http://home.schmorp.de/
1443		1671

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Comparing AnyEvent/README (file contents): Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs. Revision 1.45 by root, Fri Jul 17 14:57:03 2009 UTC

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Comparing AnyEvent/README (file contents):
Revision 1.37 by root, Mon Apr 20 14:34:18 2009 UTC vs.
Revision 1.45 by root, Fri Jul 17 14:57:03 2009 UTC